The United States and Japan will step up their defence cooperation to deal with the threat from nuclear-armed North Korea as tensions in East Asia remain high, officials from the two allies said on Thursday.

Man loses appeal over acid sentence

SYDNEY, Sept 20 AAP - A man who was jailed for at least six years for his part in a bashing and acid attack on two Sri Lankan students in Sydney's west has lost his appeal against the sentence.

Amalatheepan Srikantharajah, 28, was sentenced to a maximum 10 years in jail with a non-parole period of six years in December 2010 for two offences of aggravated break, enter and commit serious indictable offence.

The court found Srikantharajah had been part of a group of men, armed with cricket stumps, steel bars, a knife and a bottle of caustic soda, who had broken into the home of two students at Westmead in May 2009.

The attack occurred on the same day that Tamil and Sinhalese ethnic groups clashed outside Westmead railway station after Sri Lankan government forces claimed victory over Tamil rebels in the island nation's lengthy civil war.

During the Westmead attack, the two victims had holed up inside a bedroom when a member of the group poured corrosive liquid sodium hydroxide through a hole in the door, onto the two men.

One of the victims had to be placed in a medically induced coma due to severe burning to his right eye and mild burning to his left eye, burns to his throat and tongue, and other facial scarring.

In his sentencing in the District Court in 2010, Judge Martin Langford Sides accepted that while Srikantharajah had no prior knowledge that acid was being brought to the attack, he had participated in the bashing of the victims.

In an appeal on the severity of his sentence before the Court of Criminal Appeal, Srikantharajah claimed his "significant mental illness at the time of the offences" principally induced by alcohol, were not taken into account during sentencing.

But on Thursday, the appeal was dismissed for a number of reasons, among them because the appeal "did not establish definitively that he suffered from a significant mental illness, or that there was a mental condition that was of a long-term nature beyond dependence upon alcohol."

"The harm, both physical and psychological, occasioned to both victims was substantial," Justice Robert Hulme told the court.